Flame retardant polycarbonate composition

ABSTRACT

A flame retardant polycarbonate composition comprising in admixture an aromatic carbonate polymer and a flame retardant additive which may be the metal salts of sulfonic acids of monomeric and polymeric aromatic carboxylic acids and esters, and mixtures thereof.

This invention is directed to a flame retardant polycarbonatecomposition and in particular an aromatic polycarbonate containing inadmixture therewith a particular flame retardant additive which may bethe metal salts of sulfonic acids of aromatic carboxylic acids andesters, and mixtures of these.

BACKGROUND OF THE INVENTION

With the increasing concern for safety, there is a positive move towardsproviding safe materials for public and household use. One particulararea of need is that of providing flame resistant or flame retardantproducts for use by the ultimate consumer. As a result of this demand,many products are being required to meet certain flame retardantcriteria both by local and federal government and the manufacturers ofsuch products. One particular set of conditions employed as a measuringstandard for flame retardancy is set forth in Underwriters Laboratories,Inc. Bulletin 94. This Bulletin sets forth certain conditions by whichmaterials are rated for self-extinguishing characteristics.

In the art, there are many known flame retardant additives which areemployed by mixing with products to render such materialsself-extinguishing or flame retardant. Such flame retardant additiveshave been known to be employed in amounts of 5 to 20 weight percent inorder to be effective in extinguishing burning of those products whichare combustible. It has also been found that such amounts can have adegrading effect upon the base product to be rendered flame retardant,resulting in the losses of valuable physical properties of the baseproduct. This is particularly so when employing known flame retardantadditives with the base product polycarbonate resins. Many of theseknown additives have a degrading effect upon the polymer.

DESCRIPTION OF THE INVENTION

It has now been surprisingly discovered that an aromatic polycarbonatecan be made flame retardant by incorporating with the aromaticpolycarbonate minor amounts of certain additives, which additives areinert and do not degrade the aromatic polycarbonate. The particularadditive employed herein is unique in that even very minor amountsrender the aromatic polycarbonate flame retardant. The amount of theadditive employed herein can vary, preferably, from 0.01 to about 10weight percent based on the weight of the aromatic polycarbonate.

More specifically, the particular additive of this invention is themetal salt of substituted and unsubstituted sulfonic acids of aromaticcarboxylic acids and esters and mixtures of these. The metal saltemployed in the practice of this invention is either the alkali metal oralkali earth metal salt or mixtures of the metal salts. The metals ofthese groups are sodium, lithium, potassium, rubidium, cesium,beryllium, magnesium, calcium, strontium and barium.

The sulfonic acids of aromatic carboxylic acids and esters employed inthe practice of this invention can be substituted or unsubstitutedwherein the substituent consists of an electron withdrawing radical. Asemployed herein and within the scope of this invention, any of theelectron withdrawing radicals can be employed in the practice of thisinvention. However, preferably, the electron withdrawing radical orsubstituent employed in the practice of this invention is the halo-,nitro-, trihalomethyl and cyano electron withdrawing radicals ormixtures of these electron withdrawing radicals.

The electron withdrawing phenomenon, or as it is also referred to aselectronegativity, is defined in Basic Principles of Organic Chemistryby Roberts and Caserio, 1964 (pages 185-186), and Physical OrganicChemistry by Jack Hine, McGraw-Hill Book Company, Inc. 1962 (pages 5, 32and 85-93). Briefly, the electron withdrawing phenomenon is where theradical has a strong affinity for a negative charge, namely electrons,but still remains covalent and does not form an ion. This is anextremely brief description of this phenomenon and is merely set forthhere to describe the electron withdrawing effect. Reference should bemade to the texts set forth above.

In the practice of this invention, the types of sulfonic acids employedherein may be either the monomeric or the polymeric form or mixtures ofthese. When first considering the monomeric form, the metal salt of theunsubstituted and substituted sulfonic acids of aromatic carboxylicacids and esters have the following formula:

    X.sub.p R(SO.sub.3 M).sub.m (COOY).sub.n R'.sub.q          I.

wherein X is an electron withdrawing radical, M is a metal which may beselected from the periodic table of either an alkali metal or an alkaliearth metal, R is an aryl radical of 1-4 aromatic rings, R' is anorganic radical of 1-4 carbon atoms and is either alkyl, alkenyl,alkylene, alkenylene, alkylidene or alkenylidene, Y is a metal describedunder M or an organic radical of 1-20 carbon atoms and is either alkyl,cycloalkyl, aralkyl, alkenyl, cycloalkenyl, aralkenyl or aryl, m and nare integers of 1-6 and p and q are integers from 0-10.

Actually, while there are many compounds that meet the requirements ofFormula I and which offer excellent flame retardant characteristics toan aromatic polycarbonate, the preferred additive employed in thepractice of the monomeric form is sodium dimethyl2,4,6-trichloro-5-sulfoisophthalate. This has the following formula:##SPC1##

When the polymeric form of the sulfonic acids of the unsubstituted andsubstituted aromatic carboxylic acid esters is employed in the practiceof this invention, it can best be represented by the following formula:

    [Hal].sub.p [R(COO).sub.2-4 R'].sub.m [SO.sub.3 M].sub.x   II.

wherein Hal is a halogen selected from the group comprising fluorine,chlorine and bromine, R and R' are either aromatic nuclei of 1-4aromatic rings or aliphatic and cycloaliphatic radicals of from 2-20carbon atoms, provided that either R or R' must be aromatic, M is ametal which may be selected from the periodic table of either an alkalimetal or an alkali earth metal, m is an integer from 2-300, x is aninteger from 1- 600 and p is an integer from 0-600.

Actually, while there are many compounds that meet the requirements ofFormula II, including mixtures of the unsubstituted and substitutedaromatic carboxylic acid esters, and which offer excellent flameretardant characteristics to an aromatic polycarbonate, the preferredadditives employed in the practice of the polymeric form are polysodiumpolyethyleneterephthalate polysulfonate, polysodiumpolybutylene-2,5-dibromoterephthalate polysulfonate and polysodiumpolybutyleneterephthalate polysulfonate.

PREFERRED EMBODIMENT OF THE INVENTION

In order to more fully and clearly illustrate the present invention, thefollowing specific examples are presented. It is intended that theexamples be considered as illustrative rather than limiting theinvention disclosed and claimed herein. In the examples, all parts andpercentages are on a weight basis unless otherwise specified.

EXAMPLE I

Ninety-nine (99) parts of an aromatic polycarbonate, prepared byreacting 2,2-bis(4-hydroxyphenyl)propane and phosgene in the presence ofan acid acceptor and a molecular weight regulator and having anintrinsic viscosity of 0.57 is mixed with 1 part of a finely grounddehydrated additive listed in Table I by tumbling the ingredientstogether in a laboratory tumbler. The resulting mixture is then fed toan extruder, which extruder is operated at about 265°C., and theextrudate is comminuted into pellets.

The pellets are then injection molded at about 315°C. into test bars ofabout 5 in. by 1/2 in. by about 1/16-1/8 in. thick. The test bars (5 foreach additive listed in the Table) are subject to the test procedure setforth in Underwriters Laboratories, Inc. Bulletin UL-94, Burning Testfor Classifying Materials. In accordance with this test procedure,materials so investigated are rated either SE-O, SE-I or SE-II based onthe results of 5 specimens. The criteria for each SE rating per UL-94 isbriefly as follows:

"SE-O": Average flaming and/or glowing after removal of the ignitingflame shall not exceed 5 seconds and none of the specimens shall dripflaming particles which ignite absorbent cotton.

"SE-I": Average flaming and/or glowing after removal of the ignitingflame shall not exceed 25 seconds and the glowing does not travelvertically for more than 1/8 inch of the specimen after flaming ceasesand glowing is incapable of igniting absorbent cotton.

"SE-II": Average flaming and/or glowing after removal of the ignitingflame shall not exceed 25 seconds and the specimens drip flamingparticles which ignite absorbent cotton.

In addition, a test bar which continues to burn for more than 25 secondsafter removal of the igniting flame is classified, not by UL-94, but bythe standards of the instant invention, as "burns." Further, UL-94requires that all test bars in each test group must meet the SE typerating to achieve the particular classification. Otherwise, the 5 barsreceive the rating of the worst single bar. For example, if one bar isclassified as SE-II and the other four (4) are classified as SE-O, thenthe rating for all 5 bars is SE-II.

The results of the different additives within the scope of the instantinvention are as follows with a control being the aromatic polycarbonateas prepared above without the additive of the type set forth herein.

                                      TABLE 1.                                    __________________________________________________________________________                         Flame Out Time                                                                         No. of Drips                                    Additive (1.0 weight percent)                                                                      Seconds (Avg.)                                                                         Per Test Bar                                                                          Rating                                                                             Remarks                            __________________________________________________________________________       CONTROL           31.6     4+      Burns                                   Trisodium 5-sulfoisophthalate                                                                      4.1      1.4     SE-II                                   Disodium 2,5-dichloro-4-sulfobenzoate                                                              2.8      0.8     SE-II                                                                              2 test bars were SE-O              Tripotassium 3,5,6-trichloro-4-                                                                    3.1      0       SE-0                                    sulfophthalate                                                                Calcium 5-sulfoisophthalate                                                                        8.4      1.2     SE-II                                                                              1 test bar was SE-I                Sulfobromophthalein sodium                                                                         3.0      4.0     SE-II                                   Trisodium 2,4,6-trichloro-3,5-disulfo-                                                             2.8      0.8     SE-0                                    benzoate                                                                      Sodium dimethyl 5-sulfoisophthalate                                                                12.0     1.2     SE-II                                                                              2 test bars were SE-I              Sodium dimethyl 2,4,6-trichloro-5-                                                                 3.2      0.8     SE-0                                    sulfoisophthalate                                                             Calcium dimethyl 2-chloro-5-sulfoiso-                                                              4.4      0.8     SE-II                                                                              2 test bars were SE-0              phthalate                                                                     Polysodium polyethyleneterephthalate                                                               4.8      1.2     SE-II                                   polysulfonate                                                                 Polysodium polyethylene-2,5-dibromo-                                                               3.0      0.8     SE-0                                    terephthalate polysulfonate                                                   Polysodium polybutyleneterephthalate                                                               5.2      2.0     SE-II                                   polysulfonate                                                                 Polypotassium poly(dibromoneopentylene)                                                            4.6      1.6     SE-II                                   isophthalate polysulfonate                                                    Polysodium phthalic acid-glycerol-                                                                 5.8      0.8     SE-I                                    polyester polysulfonate                                                       __________________________________________________________________________

EXAMPLE II

This Example is set forth to demonstrate the effect of the flameretardant additives of this invention at the lower limits of 0.01 weightpercent based on the weight of the polymer composition.

In preparing the test bars for this Example, 99.99 parts of thepolycarbonate of Example I is mixed with 0.01 weight percent of theadditives listed in Table 2 employing the same procedure. Test bars arethen molded using the same procedure employed in Example I. The testbars are subjected to the same test procedure of Example I with thefollowing results:

                                      TABLE 2.                                    __________________________________________________________________________                         Flame Out Time                                                                         No. of Drips                                    Additive (0.01 weight percent)                                                                     Seconds (Avg.)                                                                         Per Test Bar                                                                          Rating                                                                             Remarks                            __________________________________________________________________________       CONTROL           31.6     4+      Burns                                   Trisodium 3,5,6-trichloro-4-sulfo-                                                                 5.6      3.6     SE-II                                   isophthalate                                                                  Trisodium 2,4,6-trichloro-3,5-disulfo-                                                             8.1      4.0     SE-II                                   benzoate                                                                      __________________________________________________________________________

EXAMPLE III

This Example is set forth to show the effect of a known commerciallyavailable flame retardant additive.

A.

Example I is repeated except that in place of the additives employedtherein, only 1 part 1,2,5,6,9,10-hexabromocyclododecane is used herein.The results obtained upon evaluating five (5) test bars are the same asobtained for the Control shown in Table 1 above.

B.

Part A. above is repeated but using 5 weight percent of the aboveadditive, namely 1,2,5,6,9,10-hexabromocyclododecane. The resultsobtained are the same as obtained in Part A. above.

C.

Part A. above is repeated but using 10 weight percent of the aboveadditive, namely 1,2,5,6,9,10-hexabromocyclododecane. At this level ofadditive, test bars are rated SE-II. However, the polycarbonate is badlydegraded as evidenced by severe dark streaking of the molded test bars,which degradation does not occur with the additives of the instantinvention.

EXAMPLE IV

Example III is repeated except that hexabromobiphenyl is employedherein. The results obtained are essentially the same as those ofExample III.

EXAMPLE V

Example III is repeated except that the additive employed herein is acombination of antimony oxide and a material which is a mixture ofpolychlorinated biphenyl (Aroclor by Monsanto Company). The proportionof the ingredients of the additive employed in this example is based on3 parts of chlorine per 1 part of antimony. The results obtained at 1weight percent and 5 weight percent amounts are the same as in ExampleIII.

However, at the higher amount, namely 10 weight percent, flameretardancy effect is noted, but with, again, severe degradation of thepolycarbonate, as evidenced by the substantial reduction in theintrinsic viscosity of the molded test bars. As molded, the intrinsicviscosity of the test bars with 1 weight percent of the above additiveis about 0.50. The intrinsic viscosity of the molded test barscontaining 10 weight percent of the flame retardant additive of thisExample is 0.253. This shows the severe degradation of the polycarbonatewhen employing this type of well known flame retardant.

In the practice of this invention, aromatic carbonate polymers arerendered flame retardant by the addition of certain particular additiveswhich are the metal salts of substituted and unsubstituted sulfonicacids of aromatic carboxylic acids and esters and which include mixturesof these. The amount of the additives employed in the practice of thisinvention may vary from 0.01 to up to that amount which does not causedegradation of the physical properties of the carbonate polymer. This isgenerally up to about 10 weight percent based on the weight of thearomatic carbonate polymer but may be higher. The amount of the additiveto be employed can also be a function of the degree of flame retardancydesired.

It is not exactly understood how the additive of this inventionfunctions or how such minor amounts can act as an effective flameretardant for the aromatic carbonate polymer. Analysis of thecomposition of this invention after being subjected to a firetemperature of about 600°C. showed an unusually high percentage ofremaining char. This leads one to hypothesize that the additive may actas a cross-linking agent when the aromatic carbonate polymer issubjected to fire temperatures. However, it is emphasized that this isonly theory and should not be construed as actually occurring.

As indicated previously, the additive of the instant invention comprisesthe alkali or alkali earth metal salts of the substituted andunsubstituted sulfonic acids of aromatic carboxylic acids and esters andmixtures thereof. While a great number of such salts are set forth inthe tables of the Examples of the instant invention, these are only arepresentative sample of the additives of this invention. The sodium,calcium, magnesium, potassium, strontium, lithium, barium, rubidium andcesium salts of other sulfonic acids of aromatic carboxylic acids andesters can be employed in place of those of the Examples with the sameeffective flame retardancy being achieved. These other metal salts ofaromatic carboxylic acids and esters are obtained for the followingsulfonic acids:

diethyl 4-sulfonaphthalene-2,6-dicarboxylate

dimethyl 9,10-dichloro-4-sulfo-anthracene-1,5-dicarboxylate

dimethyl 9,10-dihydroanthracene-1,5-dicarboxylate

trimethyl 5-sulfotrimellitate

methyl 1,1-dichloro-2(4'-sulfophenyl)-2-phenyl-4"-carboxylate

methyl 2,3,5,6-tetrafluoro-5-sulfobenzoate

butyl 3-trifluoromethyl-5-sulfobenzoate

terephthalic acid-cyclohexanedimethanol polyester polysulfonic acid

terephthalic acid-ethylene glycol-butanediol copolyester polysulfonicacid

succinic acid-bisphenol-A copolyester polysulfonic acid

In the practice of this invention, the additive is generally prepared bywell known methods in the art. For example, one such well known methodinvolves taking an aromatic carboxylic acid and subjecting it tosulfonation using either sulfuric acid, chlorosulfonic acid, fumingsulfonic acid or sulfur trioxide. These reactions can be carried out atroom temperature or at elevated temperatures such as about 50°C. Thesalt is then prepared by adding the proper alkaline reagent insufficient amount to make the neutral salt. The sale is then recoveredby precipitation or by distillation of the solvent.

In the case of a trihalomethyl electron withdrawing substituent, such astrifluoromethyl electron withdrawing substituent for example, it is bestto start with the prepared trifluoromethyl aromatic carboxylic acid andthen sulfonate as above, as well as preparing the salt thereof.

In the practice of this invention, any of the aromatic polycarbonatescan be employed herein. However, particularly useful are the aromaticpolycarbonates prepared by reacting a dihydric phenol, such asbisphenol-A (2,2'-bis(4-hydroxyphenyl) propane) with a carbonateprecursor. Typical of some of the dihydric phenols that may be employedin the practice of this invention are bis(4-hydroxyphenyl)methane,2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxy-3-methylphenyl)propane,4,4-bis(4-hydroxyphenyl)heptane,2,2-(3,5,3',5'-tetrachloro-4,4'-dihydroxydiphenyl)propane,2,2-(3,5,3',5'-tetrabromo-4,4'-dihydroxydiphenyl)propane,(3,3'-dichloro-4,4'-dihydroxydiphenyl)methane, Other dihydric phenols ofthe bisphenol type are also available and are disclosed in U.S. Pat.Nos. 2,999,835, 3,028,365 and 3,334,154.

In addition, the reaction is carried out with the carbonate precursor inthe presence of a molecular weight regulator, and an acid acceptor and acatalyst. The preferred carbonate precursor generally employed inpreparing carbonate polymers is carbonyl chloride. However, othercarbonate precursors may be employed and this includes other carbonylhalides, carbonate esters or haloformates.

The acid acceptors, molecular weight regulators and catalysts employedin the process of preparing polycarbonates are well known in the art andmay be any of those commonly used to prepare polycarbonates.

As stated previously, mixtures are also included within the scope of theinstant invention. These mixtures include mixtures of the various metalsalts set forth herein of the monomeric and polymeric substituted andunsubstituted sulfonic acids of carboxylic acids and of the esters. Theyalso include mixtures within either the said monomeric or polymeric formof the additive. The mixtures have shown certain advantages, as forexample, SE-O rating for 5 test bars and essentially no drips per testbar.

It will thus be seen that the objects set forth above among those madeapparent from the preceding description are efficiently attained andsince certain changes may be made in carrying out the above process andin the composition set forth without departing from the scope of thisinvention, it is intended that all matters contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:
 1. A flame retardant aromatic carbonate polymercomposition comprising in admixture an aromatic carbonate polymer and aminor amount of a metal salt of monomeric substituted and unsubstitutedsulfonic acids of aromatic carboxylic acids and esters, and mixturesthereof, wherein said metal salts thereof are selected from the groupconsisting of alkali metals an alkali earth metals, and mixtures ofthese salts and said substituent on the metal salt of the substitutedsulfonic acids of aromatic carboxylic acids and esters is selected fromthe group consisting of an electron withdrawing radical and mixtures ofelectron withdrawing radicals.
 2. The composition in claim 1 wherein themetal salt of the substituted and unsubstituted sulfonic acids ofmonomeric aromatic carboxylic acid salts and esters have the followingformula:

    X.sub.p R.sub.v (SO.sub.3 M).sub.m (COOY).sub.n R'.sub.q

wherein X is an electron withdrawing radical, M is a metal selected fromthe group consisting of alkali metals and alkali earth metals, R is anaryl radical of 1-4 aromatic rings, R' is an organic radical selectedfrom the group consisting of alkyl, alkenyl, alkylene, alkenylene,alkylidene and alkenylidene radicals of 1-4 carbon atoms, Y is a metalselected from the group consisting of alkali metals and alkali earthmetals, or an organic radical which is selected from the groupconsisting of alkyl, cycloalkyl, aralkyl, alkenyl, cycloalkenyl,aralkenyl and aryl radicals of 1-20 carbon atoms, m and n are integersof from 1-6, p and q are integers of from 0-10, and v is an integer offrom 1-10.
 3. The composition of claim 2 wherein the electronwithdrawing radical is chlorine.
 4. The composition of claim 2 whereinthe metal salt is disodium 2,5-dichloro-4-sulfobenzoate.
 5. Thecomposition of claim 2 wherein the metal salt is sodium dimethyl2,4,6-trichloro-5-sulfoisophthalate.
 6. The composition of claim 2wherein the metal salt is trisodium 2,4,6-trichloro-3,5-disulfobenzoate.